This invention relates to a microwave distillation apparatus, and vessel-biasing assembly. The invention is applicable for quick and efficient distillation of beverages, such as citrus juices, using microwave energy. For example, a common practice in the juice industry includes extracting the juice from fresh fruit, removing a substantial portion of water from the juice to form a concentrate, shipping the concentrate to a processing and testing facility, and then returning a proper amount of water back into the concentrate before delivering the juice to a grocery store or other end user.
A number of quality assurance tests are performed during rehydration of the juice concentrate, and before the juice is bottled and sold. One key test relates to the amount of volatile juice flavorings, or chemical compounds known as essence, present in the juice after shipment. This essence is generally obtained for testing through distillation.
According to one prior art distillation process, a standard electrical-resistance heating element is used to bring a juice sample to boil. A portion of the heated sample is thereby converted to vapors which pass into a condensing coil. In the condensing coil, the juice vapors are cooled and returned to a liquid state. A collection vessel collects the distillate for essence testing. As a result of these tests, the essence level is adjusted accordingly during rehydration of the juice.
This distillation process is generally time consuming and inefficient. Since the juice sample must be refrigerated prior to testing, the necessary heating time using a conventional electrical element typically requires as much as 40 minutes.
In an effort to speed up the boiling time of the sample, the Applicant discovered the advantages of using a microwave heating unit in the distillation process. The boiling time was decreased to about 4 minutes using microwave energy.
An initial embodiment of the Applicant's invention is shown in FIGS. 1 and 2. This distillation apparatus "D" utilized a conventional microwave unit "U", and a flask "F" located within the microwave unit for containing a juice sample to be distilled. The flask "F" was positioned above the floor of the microwave unit on a pedestal spacer "P". A glass connecting tube "T" extended through a top wall opening in the microwave unit "U", and into sealing engagement with a mouth of the flask "F". During heating of the juice sample, it was essential that the seal between the connecting tube "T" and the mouth of the flask "F" be maintained in order to properly obtain the distillate, and to achieve accurate testing of the essence.
To maintain this seal, the Applicant constructed the pedestal spacer "P" as shown in FIG. 2 with telescoping elements, and a resilient metal coil spring "S" for permitting biasing movement of the top of the spacer as indicated by the direction arrow Thus, when the flask "F" was placed upon the pedestal spacer "P" within the microwave unit "U" the spring "S" urged the flask "F" upwardly to create and maintain the seal between the mouth of the flask and the connecting tube "T".
The opposite end of the connecting tube "T" extended outwardly from the microwave unit, and was fixedly secured to a housing "H" mounted on the top wall of the microwave unit "U". The connecting tube "T" was connected to a vapor transfer assembly "V" and condenser assembly "C" where vapors of the heated juice sample were cooled and transformed into a liquid distillate. The distillate was captured in a conventional graduated cylinder "G" for testing.
Although this distillation apparatus was far superior to other prior art devices using electrical heating elements, it nevertheless suffered from disadvantages and limitations. One disadvantage was the use of a metal coil spring within the microwave unit. The metal spring absorbed microwave energy otherwise usable for heating the juice sample, and ultimately lost its resiliency over a relatively short period of use. Moreover, due to the relatively heavy weight of the flask, the spring was required to provide a substantial upward force to properly maintain the seal between the connecting tube and mouth of the flask. This made it difficult and awkward to insert and remove the flask from within the microwave unit.
In view of these and other problems, the Applicant modified the distillation apparatus to locate the biasing assembly outside of the microwave heating unit. The biasing assembly of the present invention acts with a greater biasing force directly upon the connecting tube, as opposed to the flask, and provides and maintains a more secure seal between the connecting tube and mouth of the flask. The flask, connecting tube, and vapor transfer assembly of the distillation apparatus reside in substantial linear alignment. Thus, the force of the biasing assembly is transferred linearly through these elements, and acts to strengthen the respective sealing connections between these elements during the distillation process. Moreover, because the metal spring is not directly exposed to microwave energy, the time required for heating the juice sample is reduced, and the useful life of the spring is extended.